Numerous devices for detecting at least one flow characteristic of a fluid medium are known from the related art. The flow characteristic may in principle be an arbitrary physically and/or chemically measurable flow characteristic. In particular, the flow characteristic may be a mass flow, in particular an air mass flow, a flow velocity, and/or a volume flow. The detection may be a quantitative and/or qualitative detection. The fluid medium may be an arbitrary gas and/or an arbitrary liquid. The fluid medium may particularly preferably be an exhaust gas of an internal combustion machine. For example, the gas may also be air in an intake system of an internal combustion machine, for example, of a motor vehicle. The present invention is described in particular hereafter with reference to hot-film air flow meters, as described, for example, in Robert Bosch GmbH: Sensoren im Kraftfahrzeug [Sensors in Motor Vehicles], 2010 edition, pages 146-148. The detection of the at least one flow characteristic of the fluid medium may relate in particular to a flow rate measurement, for example, of intake air in a motor vehicle. In this case, a thermal measuring method is preferably used. The thermal measuring method is distinguished, for example, by a direct detection of the flow characteristic, in particular a sought-after measured variable, particularly preferably the air mass, in particular by high dynamic response and/or by a broad detection range, for example, of the air mass flow.
The devices known from the related art may have some disadvantages. For example, a natural sensitivity with respect to a contamination of the device, in particular of a sensor element, may be disadvantageous. In the event of a shutdown of the internal combustion machine, for example, an internal combustion engine, gases in a crankcase of the internal combustion engine may relax. The gases, in particular oil-containing gases, may reach the device, in particular the air flow meter, via a crankcase ventilation and/or an intake manifold, and may accumulate there on the sensor element, for example. This may result in a degradation of measuring accuracy, for example. To prevent this, the sensor element may be heated, for example, during the shutdown, in particular during a shutdown case, for example, by at least one chip heater, in particular to prevent oil deposits.
A method for cleaning a measuring element around which a gas flow flows, and which contains at least one heatable element, is described in German Application No. DE 102 32 072 B4. The measuring element is accommodated on a thin diaphragm material, the diaphragm material being situated so it may oscillate. Periodic energizing, which is performed at intervals, of the at least one heatable element accelerates, via a control unit or a circuit intrinsic to the measuring element, the diaphragm material, which has locally differing coefficients of thermal expansion, in the direction of the surface normal of the diaphragm material.
Devices known from the related art, as described above, mostly have multiple disadvantages, for example, inefficient operation. Therefore, a device for detecting at least one flow characteristic of a fluid medium, which has optimum control of a heating element, for example, combined with minimization of power consumption and/or with adaptation to an available electrical voltage of a voltage supply, would be desirable.